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#61e Serial I/O and Storage (CF) (The missing module)


There are errors on the silk screen. The pluss sign on RX and TX LEDs is in the wrong position, + (5V) is in the lower position. I have also changed my mind regarding the resistor values for R8 and R9, I have changed them to 330ohm.


  • MC68B50P ACIA
  • Compact Flash 44pin IDE port
  • Crystal Oscillator 7.3728Mhz rec.
  • Baud rate 115200,8,N1 at 7.3Mhz
  • Uses only 16 I/O ports
  • 51 x 102 mm
  • RC40 bus connector


  • 1x PCB - 61e
  • 1x DIP-24 socket
  • 1x DIP16 socket
  • 1x DIP-14 socket
  • 1x 44pin IDE socket
  • 1x Compact Flash 44pin IDE adaptor
  • 1x MC68B50P ACIA
  • 1x 74HCT138
  • 1x 74HCT02
  • 1x Crystal Oscillator 7.3728 Mhz (rec.)
  • 5x 100nF capacitors
  • 3x 1k resistor (alt. 1x1k and 2x330ohm)
  • 3x 2k2 resistors
  • 3x 4k7 resistors
  • 3x LEDs
  • 1x 40 pin angled male connector
  • 1x 6 pin angled male connector
  • 4x 4 pin straight male connector
  • 3x 2 pin straight male connector
  • 4x jumpers

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This module perform 3 functions;
1) serial interface
2) bus clock
3) CF drive storage
- any of the functions may or may not be enabled.

This module is intended as a companion board to Steve Cousins SC108 CPU and memory board (but works also with SC114 SBC). These two modules will form a complete kit with 64k RAM and CF storage, running CP/M fully.
An added bonus, with this module the speed on SC108 can be increased to any speed up to 24Mhz.
Small Computer Central - SC108

Recommended setup for a complete CP/M computer:
61c The missing Module (Serial, Clock and Storage)
SC108 Z80 CPU and Memory Module
SC116 3-slot backplane
optional: VGA Serial Terminal Kit with USB